1. Field of the Invention
This invention relates to a method for forming a contact hole in a semiconductor device, and more particularly, to a method for forming a contact hole by utilizing an etch barrier layer in the semiconductor device. The barrier prevents current leakage or an electrical short circuit between an underlying conductive material layer, a portion of which is unintentionally exposed in the contact hole due to excessive etching of insulating films formed on the underlying conductive material layers or to inaccurate etching resulting from mask misalignment during the fabrication process and conductive material which is placed into the contact hole.
2. Information Disclosure Statement
The area of a contact hole or via hole used in the process for manufacturing semiconductor devices has been reduced as the integrity of semiconductor device increases, thereby resulting in increasing the aspect ratio of the contact hole or via hole.
In the prior art, when a contact hole or via hole is formed between MOSFETs or on the MOSFET and to electrically connect a conductive material layer to the MOSFET through the contact hole or via hole, many kinds of etching methods, which can smooth a step coverage of the conductive material layer deposited in the contact hole, for example, an etching method in the form of the combination of isotropic etching and anisotropic etching of the insulating film positioned where the contact hole is to be formed, an etching method which utilizes the flowing of a portion of the top of the insulating film after anisotropic etching of the insulating film, an anisotropic etching method which transfers the rounded photoresistive pattern for contact mask to the insulating film, etc. can be utilized.
Specifically, as illustrated in FIG. 1A, the etching method in the form of the combination of isotropic etching and anisotropic etching etches away a potion of the insulating film 7, which protects the conductive material layer 6A, 6B, due to the excessive etching of the third insulating film 9 during the isotropic etching to smooth the step coverage of the conductive material layer to be formed on the third insulating film 9 by the rounding of the portion of insulating film positioned where the contact hole is formed, thereby causing a short circuit between the conductive material layers 6A, 6B and a conductive material 11 if another conductive material layer 11 as illustrated in dotted line in FIG. 1A is deposited on the entire surface of the structure.
Also, if the contact mask is misaligned as illustrated in FIG. 1B and the third insulating film 9 is then isotropically etched, a portion, for example, the portion "B", of the second insulating film 7 is excessively etched away, thereby exposing a portion of the conductive material layer 6A, which also results in a short circuit between the conductive material layer 6A and a conductive material layer 11 to be formed later.
Unlikely, even though a portion of the conductive material layer 6A, 6B is not exposed, if the second insulating film 7 does not have sufficient thickness so that it cannot exhibit the desired insulating effect, current leakage occurs between the conductive material layer 6A, 6B and a conductive material layer 11 to be formed on the entire surface of the structure. Thus, it may result in the malfunction of the semiconductor device.
Therefore, it is an object of the present invention to provide a method for forming a contact hole by utilizing an etch barrier layer having a significantly different etching selectivity from the insulating film formed on the etch barrier layer in order to prevent the conductive material layer underlying the insulating film from being exposed due to the excessive etching of the insulating film positioned where the contact hole is formed, or to prevent a portion of the insulating film from being partially etched due to the contact mask misalignment as well as maintaining a predetermined thickness of the insulating film between the conductive material layers when the etching process is performed.